CVE-2025-71295

In the Linux kernel, the following vulnerability has been resolved:

fs/buffer: add alert in trytofree_buffers() for folios without buffers

trytofreebuffers() can be called on folios with no buffers attached when filemapreleasefolio() is invoked on a folio belonging to a mapping with ASRELEASEALWAYS set but no releasefolio operation defined.

In such cases, folioneedsrelease() returns true because of the ASRELEASEALWAYS flag, but the folio has no private buffer data. This causes trytofreebuffers() to call dropbuffers() on a folio with no buffers, leading to a null pointer dereference.

Adding a check in trytofreebuffers() to return early if the folio has no buffers attached, with WARNON_ONCE() to alert about the misconfiguration. This provides defensive hardening.